Communications Biology (Jan 2024)

Different ways of evolving tool-using brains in teleosts and amniotes

  • Pierre Estienne,
  • Matthieu Simion,
  • Hanako Hagio,
  • Naoyuki Yamamoto,
  • Arnim Jenett,
  • Kei Yamamoto

DOI
https://doi.org/10.1038/s42003-023-05663-8
Journal volume & issue
Vol. 7, no. 1
pp. 1 – 15

Abstract

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Abstract In mammals and birds, tool-using species are characterized by their relatively large telencephalon containing a higher proportion of total brain neurons compared to other species. Some teleost species in the wrasse family have evolved tool-using abilities. In this study, we compared the brains of tool-using wrasses with various teleost species. We show that in the tool-using wrasses, the telencephalon and the ventral part of the forebrain and midbrain are significantly enlarged compared to other teleost species but do not contain a larger proportion of cells. Instead, this size difference is due to large fiber tracts connecting the dorsal part of the telencephalon (pallium) to the inferior lobe, a ventral mesencephalic structure absent in amniotes. The high degree of connectivity between these structures in tool-using wrasses suggests that the inferior lobe could contribute to higher-order cognitive functions. We conclude that the evolution of non-telencephalic structures might have been key in the emergence of these cognitive functions in teleosts.